Insulating body



Patented Mar. 7, 1933 UNITED STATES PATENT foFFIcE GEORGE E. ELLIS, OF ST. PAUL, MINNESOTA, ASSIGNOB TO THE INSULIN COMPANY, OF MINNEAPOLIS, mNESOTA, A CORPORATION OF MINNESOTA.

msuna'rnm BODY ll'o Drawing.

This invention relates to the production of insulating bodies, and objects are: to produce such bodies which are tough, strong and flexible; to produce bodies having a low resonance with toughness, and with 01 without flexibilitiy; to produce relatively light weight but stifi' bodies having relatively great non-resonance; to produce light weight bodies by simultaneously pressing and heating dry products of lower specific gravity; to produce both laminated and unlaminated insulating bodies; to produce insulating bodies of lowresonance, from dry spongy air-filled porous slabs of cellulosic or other fibrous material; to cheaply produce insulating bodies; to .reduce time of'production; and generally to produce insulating bodies having a maximum insulating ability with a minimum of weight, combined with a certain amount of bendability.

Objects, features and advantages will appear, in the description.

An important object is to produce a hard, stifi somewhat bendable board simulating lumber, by submitting cellulose or other fiber to. heat and pressure.

In carrying out the process, any suitable fiber, such as wood, including poplar, spruce, jack pine or any sawmill waste or forest waste is fiberized, for example, by the grindstone process. The fiberization is controlled so that as long a fibe'r as possible is produced, in fact too long and too coarse a fiber for the coarsest grade ofpaper. (This is a much cheaper way than ordinary, for producing pulp.) The pulp is then well hydrolized, and run from the pulper into any suitable machine such as a cylinder felting machine, of the type shown in, my

' Patent Number 1,67 2,249 June 5th, 1928 for apparatus for making composition boards orsheets.

From the felting machine the pulp is delivered to and run through a roller press,

the function of which is to remove a major fibrous materials including cellulosic, may

Application filed August 10, 1929. Serial Hp. asaoaa.

portion of the water from the sheet, material, prior to its passage through a dryer.- The thickness of the sheet is regulated by varying the percentage uantity of the water to pulp stock. The ying is accomplished by heat without pressure, and leaves the sheet in a spongy, air-filled condition, and so as to have the maximum amount of air retained. In other words, to make the sheet porous and non-resonant. The next step in theprocess is to simultaneously press and heat the felted product during which operation a kind of vulcanization seems to take place. As the pressures are increased the amount of heat may be decreased and vice versa. Thus far the best product is madeby three hundred pounds pressure per square inch with a temperature equivalent to one hundred twenty pounds of steam pressure for about thirty minutes. The resulting product has substantial tensile strength combined with flexibility suflicient to permit not too abrupt bending.

It has been found that various kinds of be used for making the product herein claimed, and including licorice root as a waste orby-product ,from the extraction of licorice. Cellulosic materials which contain ninety-nine per cent of pure cellulose are also usable to make a good bendable. sound a jinsulating board.

The pressing and heating while dry is advantageous because the light weight product produced by the first series of steps can be finished at the factory, and can then be shipped to distant points or to the distributing points, and then made into harder, flexible (or inflexible boards by the use of hot presses of small size well adapted for small quantity production. Moreover, time is saved because instead of taking two hours or more to force water. out of a wet product by pressure and heat (as is ordinarily done), the same quantity can be produced by the process herein in about ten minutes. Another advantage is that it is not necessary to produce the very hard product ordinarily had as the result of unusual heats and pressures required to dry a wet sheet.

Another advantage of the present process is that the product produced by the first series of steps, after having been run through a roller press to ex-press a portion of the water, is then run through the dryer. It is much cheaper to dry, and then press and heat this dry product because the original drying only requires about two hours, and because a roller dryer of about three hundred feet in length can be used and about four hundred twenty-one thousand square feet of material delivered by the felting machine can be passed through the dryer in a day. A great advantage for quantity production. When making very much harder boards, and with the use of hydraulic presses, the production is only about twenty thousand square feet per day.

The cost of large roller presses of the capacity above mentioned is less than a number of small hydraulic presses, and the labor is more on the smaller presses because the limber wet sheet (as distinguished from the dry sheet herein) has to be handled on trays which trays are covered with wire screens and fed to the machine but have to be lifted manually and placed in the press. Another advantage of the present invention is, as before mentioned, that the thick, light density product can be shipped to the distributing point and can then be made into hard board by the use of hot presses for small quantity production.

After many experiments it has been found that the formation of the light density product and the squeezing and roller drying of this product without pressure but with heat, and then the subsequent treatment while dry with pressure and heat simultaneously gives a product having very much improved physical properties and apparently certain new chemical properties, heretofore unknown in material which is sound-proof, relatively hard and tough, and yet can be bent substantially without fracture.

This second step produces a relatively hard, flexible board product adapted for lining Walls in lieu of lath and plaster; and

for panel work of all kinds, namely: furniture lining, cabinet work, and automobile lining.

It is believed that a kind of vulcanization takes place in which the pressure and heat fuses the cementing materials of the wood. The specific gravity after the second operation ranges from .7 to .85 and'the tensile strength is raised from about three hundred to about twelve hundred. The qualities are toughness and flexibility, the latter quality permitting a curving, not too abruptly.

The material is less resonant than the ordinary so-called hard boards yet is strong enough to be used under conditions where.

harder and heavier, and, therefore, more expensive board has heretofore been believed necessary. Tests show that the product combines a maximum toughness, flexibility and strength with a minimum of weight and resonant quality.

Another advantage in dry pressing, is that the pressing time is more uniform because there is no question of pressing until there is absence of steam, as in the case Where the material is pressed wet.

The felted product is about half an inch thick and the re-pressed, dry product is three-eighths, five-sixteenths, one-fourth or three-sixteenths, according to the use.

To recapitulate: The thick felted dry material which is about half an inch thick or may even be thicker, can be pressed in a standard hot plate hydraulic press with suflicient pressure employed to press the product to one-half or less of its original thickness, maintaining the pressure and temperature as before mentioned for a period of time sufficient to fuse or partly fuse some of the cellulosic constituents into a relatively stifi' hard board with a tensile strength about three times greater than before pressing. In regard to tensile strength, this depends somewhat upon the amount of pressure, the time and the temperature. If great hardness and tensile strength are desired, it follows that the pressure, temperature and time should be lengthened. It has been found that in some cases a hard, inflexible board three-sixteenths of an inch thick which is impervious to water and which has a tensile strength of over two thousand pounds per square inch of area can be produced from a pressure of three hundred-pounds per square inch at a temperature of 350 F. for fifteen hours. This is a few ture.

The product of the first steps is about half an inch thick, has a specific gravity of from .2 to .3, and the product after the second series of steps of dry pressing, etc., with heat has a specific gravity of from .7 to .8. The tensile strength of the product of the first series of steps is about three hundred pounds per square inch, while the tensile strength of the flexible product of the second series of steps is about twelve hundred pounds.

Products substantially corresponding to the specifications above set forth are produced by pressing at nine hundred pounds per square inch and heating at 285 to 300 F. This product also has a maximum tensile strength and stiffness along with the nonresonant quality and with suflicient flexibility to permit a certain amount of not too abrupt bending.

The air-filled product is also made by feltin wood fiber, and the felting is accomphshed ona cylinder machine of the type ordinarily used for making wrapping paper automobile linings. Their qualities are: toughness and flexibility, the latter quality permitting it to be bent, not too abrupitllly and substantially without fracture. e products although still and having considerable tensile strength, are less resonant than a or drumming, and yet they are strong harder boards, so that there is no rattling enough to be used under conditions where harder, heavier and therefore more'expensive boards have heretofore been believed necessary. The products combine maximum toughness, flexibility and strength, with a minimum of weight and resonant quality.

Certain of the products herein, having the qualities above mentioned, have been produced as the result of extended experiment within certain ranges of pressure, heat, length of time of applied pressure and heat, tensile strength and specific gravity. The intention is, therefore, to claim a series of products having tensile strengths approximately within the range of three hundred to two thousand pounds per square inch; to claim specific gravities ranging approximately from .2t0 .8; to claim application of ressures ranging approximately from nine hundred to twelve hundred pounds per square inch; to claimap lication of heats ranging from approximate y 285 to approximately 300 F.; to claim length of time of applied pressures and heat ranging substantially from ten minutes to one hour, to produce bodies having thicknesses ranging from substantially one half to substantially three-sixteenths of an inch. It is the intention to claim all products within these ran es, as well as various combinations within t e ranges set forth. Excellent products have beenproduced by applying three hundred pounds pressure, at a heat the equivalent of about one hundred twenty pounds of steam for about half an hour.

I claim as my invention:

1. A process for making .thiek heat insulating bodies which consists in fiberizing wood to produce a coarse fiber too long an too coarse for the coarsest grade of paper, hydrolizing the pulp, forming the pulp into a thick felted sheet, drying, and then simultaneously product while dry.

2. A process for making thick heat insubodies which consists in fiberizin latin Wood to produce a coarse fiber too long an latin pressing and heating the felted too coarse for the coarsest; grade of paper,

3. A rocess for making thick heat insulating dies which consists in fiberizing hydrolizing the pulp formm the 111 mto' .a thick felted sheet, and then eat dryihg raw wood to produce a coarse fiber too long 4 and too coarse for the coarsest grade of par, hydrolizing the pulp, forming the pulp nto a thick felted sheet, and then heat drymg. 7

4. A process for making thick heat insuh drolizing the pulp, forming a thi felted s eet, heat drying, and then simultaneously pressing and heating the dry felted product at a pressure of approximately three hundred pounds per square inch and at a temperature substantially equivalent to one hundred twenty pounds of steam pressure, for approximately thirty minutes.

5. A process for making thick heat insulating bodies which consists in fiberizing raw wood, hydrolizing the pulp, forming a thick felted sheet, heat dr 'ng and then simultaneously pressing an heating the dry felted product'at a pressure of approximately three hundred pounds per square inch and at a temperature substantially equivalent to one hundred twenty pounds of steam pressure, for approximately thirty minutes.

6. A process or making a thick heat insulating body which consists in fiberizing raw wood, hydrolizing thepulp, forming a thick felted air-filled sheetapproximately half an inch thick, drying, then simultaneously pressing and heatin the substantially dry felted product to r uce it to a thickness within the range of three-eighths to three-sixteenths of an inch, by a pressure of approximately three hundred pounds per square inch, and at temperatures within the range of two hundred eighty-five to three hundred degrees Fahrenheit, for from ten to sixty minutes. 1

7. A process for making thick heat insulating bodies which consists in fiberizingraw wood to produce a fiber too long an too coarse for the. coarsest grade of paper, hydrolizing the pulp, forming the pulp into a felted sheet about one-half an inch thick,

drying, then simultaneously pressin and heatinithe dry felted product to re uce it to a t 'ckness within the range of threeeighths to three-sixteenths of an inch, to produce a product havinga specific gravity within the range of .7 to .85, the ap lied temperature bemg within the range 0 twohundred eighty-five to three hundred debodies which consists in fiberizing so H thick air-filled sheet, drying to remove the major portion of the water, and then simultaneously pressing and heating at a pressure not substantially less than three hundred pounds per square inch and at a temperature within the range of two hundred eighty-five to three hundred degrees Fahrenheit, and the pressing time ranging between ten to sixty minutes.

In witness whereof, I have hereunto set my hand this 6th da of August 1929.

G ORGE H. ELLIS. 

